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The search for a superconductor that can function in less extreme conditions than hundreds of degrees below zero or at pressures such as those near the center of the Earth is the search for a revolutionary new power, needed for the magnetic levitation cars and ultra-efficient power grids of the future.
But developing this kind of “room temperature” superconductor is a feat science has yet to achieve.
A researcher at the University of Central Florida, however, is working to bring this goal closer to realization, with some of his latest research published recently in the journal Communications physics – Nature.
In the study, Yasuyuki Nakajima, assistant professor in the UCF Department of Physics, and co-authors showed they can take a closer look at what is happening in “strange” metals.
These “strange” metals are special materials that exhibit unusual thermal behavior in electrical resistance. The “strange” metallic behavior is found in many high-temperature superconductors when they are not in a superconducting state, making them useful to scientists studying how some metals become superconducting at high temperatures.
This work is important because understanding the quantum behavior of electrons in the “strange” metal phase could allow researchers to understand a mechanism for superconductivity at higher temperatures.
“If we know the theory to describe these behaviors, we might be able to design high-temperature superconductors,” says Nakajima.
Superconductors get their name because they are the last conductors of electricity. Unlike a conductor, they have zero resistance, which, like an electronic “friction,” causes electricity to lose power as it flows through a conductor such as copper or gold wire.
This makes superconductors a dream material for supplying energy to cities as the energy saved using resistance-free cables would be enormous.
Powerful superconductors can also levitate heavy magnets, paving the way for practical and economical magnetic levitation cars, trains and more.
To turn a conductor into a superconductor, the metallic material must be cooled to an extremely low temperature to lose all electrical resistance, an abrupt process that physics has yet to develop a complete theory to explain.
These critical temperatures at which the switch is made are often between -220 and -480 degrees Fahrenheit and typically result in an expensive and cumbersome cooling system that uses liquid nitrogen or helium.
Some researchers have obtained superconductors that function at around 59 degrees Fahrenheit, but were also at a pressure more than 2 million times that on the Earth’s surface.
In the study, Nakajima and the researchers were able to measure and characterize the behavior of electrons in a “strange” metallic state of non-superconducting material, an iron pnictide alloy, near a quantum critical point where electrons pass through a predictable individual behavior to collectively moving in quantum mechanical fluctuations that are difficult for scientists to theoretically describe.
The researchers were able to measure and describe the behavior of electrons using a unique metal mixture in which nickel and cobalt were substituted for iron in a process called doping, thus creating a pnictide alloy of iron that does not superconduct down to -459. , 63 degrees Fahrenheit, far below the point where a conductor would typically become a superconductor.
“We used an alloy, a relative compound of superconducting iron based at high temperature, in which the ratio between the components, iron, cobalt and nickel in this case, is fine-tuned so that there is no superconductivity even close to the absolute zero, “Nakajima says. “This allows us to access the critical point where quantum fluctuations govern the behavior of electrons and to study how they behave in the compound.”
They found that the behavior of electrons was not described by any known theoretical prediction, but that the scattering rate at which electrons were transported through the material may be associated with what is known as Planck dissipation, the quantum speed limit on the velocity of matter. transport energy.
“The quantum critical behavior we have observed is quite unusual and differs completely from the theories and experiments for known quantum critical materials,” says Nakajima. “The next step is to map the doping phase diagram in this iron pnictide alloy system.”
“The ultimate goal is to design superconductors at higher temperatures,” he says. “If we can do that, we can use them for MRI scans, magnetic levitation, power grids and more, at low cost.”
Unlocking ways to predict the resistance behavior of “strange” metals would not only improve the development of superconductors, but would also inform the theories behind other phenomena at the quantum level, Nakajima says.
“Recent theoretical developments show surprising connections between black holes, gravity and quantum information theory through Planck dissipation,” he says. “So, the search for” strange “metallic behavior has also become a hot topic in this context.”
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